Catalysts for producing carboxylic acid salts

ABSTRACT

Catalysts for preparing carboxylic acid salts from alcohols which a) consist of copper or b) comprise from 99.9 to 10% by weight of copper and from 0.01 to 90% by weight of iron and from 0 to 50% by weight of one or more other metals, and may optionally be doped, the hydroxides being obtained by precipitation of copper salt solutions or by coprecipitation of copper and iron salt solutions optionally containing salts of other metals using a base, and being reduced by hydrogen.

The present invention relates to catalysts for preparing carboxylic acidsalts based on copper.

WO-A1-94/24091 discloses catalysts for preparing aminocarboxylic acidsalts by coprecipitating salts of copper and zirconium with salts ofchromium, titanium, niobium, tantalum, vanadium, molybdenum, magnesium,tungsten, cobalt, nickel, bismuth, tin, antimony, lead and germanium.

However, these catalysts leave something to be desired.

It is an object of the present invention to provide improved catalystsfor preparing carboxylic acid salts.

We have found that this object is achieved by novel and improvedcatalysts for preparing carboxylic acid salts from alcohols which

-   a) consist of copper or-   b) comprise from 99.9 to 10% by weight of copper and from 0.01 to    90% by weight of iron and from 0 to 50% by weight of one or more    other metals,    and may optionally be doped, characterized by the hydroxides being    obtained by precipitation of copper salt solutions or by    coprecipitation of copper and iron salt solutions optionally    containing salts of other metals using a base, and being reduced by    hydrogen.

The catalysts according to the invention may be obtained as follows:

A copper salt solution may be precipitated or a mixture of a copper saltsolution and an iron salt solution and optionally salt solutions ofother metals may be coprecipitated, batchwise or continuously, with abase in the pH range of from 7 to 14 at temperatures of from 5 to 100°C., preferably from 15 to 90° C., more preferably from 20 to 85° C., anda pressure of from 0.1 to 5 bar, preferably atmospheric pressure, andthe precipitation or coprecipitation product, generally thecorresponding hydroxides, may be, for example, washed with water, driedat from 50 to 250° C., optionally calcined at from 300 to 700° C. andthen reduced at from 150 to 300° C. in a hydrogen stream. However, thereduction may also take place before calcining and, if necessary,calcining may be repeated.

The copper or copper/iron catalysts may be doped after coprecipitationor after the subsequent drying or after calcining by impregnation,electroless deposition, electrochemical deposition, CVD (chemical vapordeposition) or sputtering, preferably impregnation or electrolessdeposition, more preferably impregnation. Useful elements for dopinginclude those referred to as “other metals” which may be applied in theform of soluble salts or as the metals themselves. When salts areapplied, subsequent calcining is generally used for fixing. The dopantquantity may vary within a wide range, but it is generally from 0.001 to5% by weight, preferably from 0.005 to 3% by weight, more preferablyfrom 0.01 to 2% by weight, in particular from 0.02 to 1% by weight.

Examples of useful bases include alkali metal hydroxides, alkaline earthmetal hydroxides, alkali metal carbonates, alkaline earth metalcarbonates, alkali metal hydrogencarbonates, alkaline earth metalhydrogencarbonates, ammonia, water-soluble amines or mixtures thereof.Useful alkali metal hydroxides include lithium hydroxide, sodiumhydroxide, potassium hydroxide, rubidium hydroxide, and cesiumhydroxide, preferably lithium hydroxide, sodium hydroxide, and potassiumhydroxide, more preferably sodium hydroxide, and potassium hydroxide.Useful alkaline earth metal hydroxides include beryllium hydroxide,magnesium hydroxide, calcium hydroxide, strontium hydroxide, and bariumhydroxide, preferably magnesium hydroxide and calcium hydroxide, morepreferably calcium hydroxide. Useful alkali metal carbonates includelithium carbonate, sodium carbonate, potassium carbonate, rubidiumcarbonate, and cesium carbonate, preferably lithium carbonate, sodiumcarbonate, and potassium carbonate, more preferably sodium carbonate,and potassium carbonate. Useful alkaline earth metal carbonates includeberyllium carbonate, magnesium carbonate, calcium carbonate, strontiumcarbonate, and barium carbonate, preferably magnesium carbonate andcalcium carbonate, more preferably calcium carbonate. Useful alkalimetal hydrogencarbonates include lithium hydrogencarbonate, sodiumhydrogencarbonate, potassium hydrogencarbonate, rubidiumhydrogencarbonate, and cesium hydrogencarbonate, preferably lithiumhydrogencarbonate, sodium hydrogencarbonate, and potassiumhydrogencarbonate, more preferably sodium hydrogencarbonate, andpotassium hydrogencarbonate. Useful alkaline earth metalhydrogencarbonates include beryllium hydrogencarbonate, magnesiumhydrogencarbonate, calcium hydrogencarbonate, strontiumhydrogencarbonate, and barium hydrogencarbonate, preferably magnesiumhydrogencarbonate and calcium hydrogencarbonate, more preferably calciumhydrogencarbonate. Examples of useful water-soluble amines includeammonia, methylamine, dimethylamine, trimethylamine, ethylamine,diethylamine and triethylamine, preferably ammonia, dimethylamine,trimethylamine and triethylamine, more preferably ammonia andtrimethylamine.

Useful other metals include all metals of the groups IIa, IIIa, IVa, Va,VIa, IIb, IIIb, IVb, Vb, VIIb, VIIb and VIII of the Periodic Table, suchas beryllium, magnesium, calcium, strontium, barium, boron, gallium,indium, thallium, germanium, tin, lead, antimony, bismuth, selenium,tellurium, silver, gold, zinc, cadmium, scandium, yttrium, lanthanum,titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum,tungsten, manganese, technitium, rhenium, cobalt, nickel, ruthenium,rhodium, palladium, osmium, iridium and platinum, and also cerium,preferably nickel, cobalt, chromium, zinc, lanthanum, ruthenium,rhodium, palladium, iridium and platinum, more preferably nickel,cobalt, zinc and lanthanum.

Useful salts of copper, iron and the other metals generally include allpreferably water-soluble inorganic and organic salts.

Useful copper salts generally include all preferably water-solubleinorganic and organic salts, for example copper nitrate, copperchloride, copper sulfate, copper carbonate, copper hydrogencarbonate,copper hydrogensulfate, copper acetylacetonate and copper acetate,preferably copper nitrate, copper chloride, copper carbonate and copperacetate, more preferably copper nitrate, copper chloride and copperacetate.

Useful iron salts generally include all preferably water-solubleinorganic and organic salts, for example iron nitrate, iron chloride,iron sulfate, iron hexacyanoferrate, iron carbonate, ironhydrogencarbonate, iron hydrogensulfate, iron acetylacetonate and ironacetate, preferably iron nitrate, iron chloride and iron acetate, morepreferably iron nitrate and iron chloride.

Useful salts of other metals generally include all preferablywater-soluble inorganic and organic salts, for example nitrates,halides, sulfates, cyanides, hydroxides, carbonates, hydrogencarbonates,hydrogensulfates, acetylacetonates and acetates, preferably nitrates,halides, sulfates, carbonates, hydrogencarbonates and acetates, morepreferably nitrates, halides, carbonates and acetates.

Depending on the origin of the starting material, the copper catalystsmay contain impurities. In general, no purification is carried out.

The copper/iron catalysts comprise from 99.9 to 10% by weight,preferably from 95 to 20% by weight, more preferably from 90 to 30% byweight of copper, from 0.01 to 90% by weight, preferably from 3 to 75%by weight, more preferably from 5 to 60% by weight of iron and from 0 to50% by weight, preferably from 0.1 to 35% by weight, more preferablyfrom 0.5 to 25% by weight of one or more other metals, ie from one toeight, preferably from one to five, more preferably from one to threeand in particular one or two other metals.

Greater preference is given to such catalysts which, as well as copper,comprise from 1 to 90% by weight of iron and are precipitated using NaOHat from pH 10 to 11.5 and a temperature of from 50 to 80° C., dried atfrom 180 to 220° C., calcined at from 450 to 550° C. and reduced usinghydrogen at from 200 to 300° C. After reduction using hydrogen, thesecatalysts comprised a copper(II) oxide and/or copper(I) oxide content offrom 0 to 35% by weight. A particular embodiment employs a catalysthaving an aluminum content of less than 4% by weight, preferably from3.99 to 0% by weight, more preferably from 3.99 to 1% by weight, inparticular from 3.99 to 2% by weight. A further particular embodimentinvolves preparing the catalyst without zirconium.

Preference is given to preparing carboxylic acid salts from alcoholsusing such catalysts according to the invention which, before reductionusing hydrogen, have a CuO crystal size of from 1 to 75 nm, morepreferably from 2 to 50 nm.

The process for preparing carboxylic acid salts from alcohols accordingto the invention may be carried out as follows:

A pressure vessel, eg an autoclave, a tube reactor, a circulationreactor or a stirred tank battery may be charged in any desired sequencewith alcohol, base, water and catalyst. The base is preferably dissolvedin water before charging. Preference is given to initially charging thecatalyst and then adding the alcohol separately from the aqueous base,or the alcohol together with the aqueous base. The closed pressurevessel is heated to a temperature of from 120 to 280° C., preferablyfrom 140 to 240° C., more preferably from 150 to 220° C., resulting inan autogenous pressure which may be increased if required. The reactiontakes place at a pressure in the range from the vapor pressure of thewater to 75 bar, preferably from 2 to 50 bar, more preferably from 3 to30 bar, in particular from 4 to 15 bar. In a particular embodiment ofthe production process, the reaction mixture comprises less than 4000ppm, preferably from 3999 to 0 ppm, more preferably from 3999 to 1000ppm, in particular from 3999 to 2000 ppm of aluminum ions.

Useful alcohols include ethylene glycol (derivatives) such as ethyleneglycol oligomers or polymeric ethylene glycols and aminoalcohols such asethanolamine, diethanolamine, triethanolamine,N,N-bis(2-hydroxyethyl)isopropylamine ortetrakis(hydroxyethyl)1,2-propylenediamine. Particularly useful alcoholshave the general formula R—CH₂CH₂OH (I).

The radicals R, R¹ and R² in the alcohols of the general formula (I) aredefined as follows:

-   R —(OCH₂CH₂OH) or —NR¹R², preferably —NR¹R²,-   R¹ and R² are each independently    -   hydrogen,    -   phenyl,    -   —CH₂CH₂OH,    -   C₁- to C₂₀-alkyl, preferably C₁- to C₈-alkyl, more preferably        C₁- to C₄-alkyl such as methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl and tert-butyl, in particular        methyl and ethyl,    -   C₂- to C₅-dialkylamino such as dimethylamino, ethylmethylamino,        diethylamino, ethyl-n-propylamino, ethyl-iso-propylamino,        methyl-n-propylamino, methyl-iso-propylamino,        methyl-n-butylamino, methyl-iso-butylamino,        methyl-sec-butylamino and methyl-tert-butylamino, preferably        dimethylamino, ethylmethylamino, diethylamino,        ethyl-n-propylamino, ethyl-iso-propylamino, methyl-n-propylamino        and methyl-iso-propylamino, more preferably dimethylamino,        ethylmethylamino, diethylamino and ethyl-n-propylamino.

Aminocarboxylic acids and salts thereof (I) are useful intermediates forchelating agents, for example, in detergents, pharmaceuticals,agrochemicals such as pesticides, and also food and feed additives.Oxycarboxylic acids and salts thereof (I) prepared from ethylene glycol(derivatives) are useful intermediates for, for example, detergents.

EXAMPLES Inventive Example 1

2.5 liters of an aqueous solution of 593 g of sodium carbonate werecontinuously introduced at 70° C. within 20 min with stirring into 2.5liters of an aqueous solution of 1536.3 g of copper nitrate at pH 7(with addition of HNO₃). After continued stirring at 70° C. for 30minutes, filtering off, washing with a total of 100 liters of water anddrying at 200° C. for 4 h, reduction was effected using hydrogen at 230°C. for 4 h.

The catalyst obtained had a copper content of 96.5% by weight and acuprite content of 3.5% by weight. The CuO crystal size before reductionusing hydrogen was 25 nm.

Inventive Example 2

4 liters of an aqueous solution of 948.8 g of sodium carbonate werecontinuously introduced at 70° C. within 35 min with stirring into 2.5liters of an aqueous solution of 1536.3 g of copper nitrate at pH 9(with addition of HNO₃). After continued stirring at 70° C. for 30minutes, filtering off, washing with a total of 100 liters of water anddrying at 200° C. for 4 h, reduction was effected using hydrogen at 230°C. for 4 h.

The catalyst obtained had a copper content of 97% by weight and acuprite content of 3% by weight. The CuO crystal size before reductionusing hydrogen was 28 nm.

Inventive Example 3

2 liters of an aqueous solution of 660 g of sodium hydroxide werecontinuously introduced at 70° C. within 20 min with stirring into 2.5liters of an aqueous solution of 1536.3 g of copper nitrate at pH 11(with addition of HNO₃). After continued stirring at 70° C. for 30minutes, filtering off, washing with a total of 100 liters of water anddrying at 200° C. for 4 h, reduction was effected using hydrogen at 230°C. for 4 h.

The catalyst obtained had a copper content of 92% by weight and acuprite content of 8% by weight. The CuO crystal size before reductionusing hydrogen was 21 nm.

Example 4 (Non-Inventive)

Inventive example 3 was repeated to produce a precipitated materialwhich was filtered off and washed. The precipitated material was thendried at 150° C. for 4 h.

50 g of the dried precipitated material was impregnated according to itswater takeup of 1.00 ml/g with 50 ml of an aqueous solution of 8.95 g ofiron (III) nitrate hydrate within 1 h. Drying was then effected at 120°C. for 4 h, calcining at 500° C. for 2 h and reduction using hydrogen at230° C. for 4 h.

The catalyst obtained had an iron content of 3% by weight. The CuOcrystal size before reduction using hydrogen was 20 nm.

Inventive Example 5

2274 g of a 40% by weight aqueous solution of sodium hydroxide werecontinuously introduced at 70° C. with stirring into 2.5 liters of anaqueous solution of 1238.7 g of copper nitrate and 357.9 g of iron (III)nitrate nonahydrate within 20 min. After continued stirring at 70° C.for 30 minutes, filtering off, washing with a total of 100 liters ofwater and drying at 200° C. for 4 h, reduction was effected usinghydrogen at 230° C. for 4 h.

The catalyst obtained had a copper content of 72% by weight. The CuOcrystal size before reduction using hydrogen was 9 nm.

Inventive Example 6

Example 5 was repeated to produce a catalyst which had a copper contentof 44% by weight by increasing the amount of iron salt used. The CuOcrystal size before reduction using hydrogen was 10 nm.

Inventive Example 7

Example 5 was repeated to produce a catalyst which had a copper contentof 10% by weight by increasing the amount of iron salt used. The CuOcrystal size before reduction using hydrogen was 13 nm.

Comparative Example A

Example 19 of WO-A-94/24091 was repeated to produce a catalyst.

Hydrogenation Procedure

An autoclave having an internal volume of 300 ml was charged with 40 gof diethanolamine, 32 g of sodium hydroxide, 85 g of water and 4 g ofthe relevant catalyst. The reaction was carried on at a temperature of170° C. and a constant pressure of 9 bar until hydrogen formation hadended. The amount of hydrogen released was recorded as a function of thereaction time. After the end of the reaction, the reaction product wasanalyzed. The results are summarized in the following table: TABLEReaction Reaction Conversion Selectivity Catalyst cycles time [min] [%][%] Inventive 1 164 99 98 example 3 Example 4 1 176 99 98 Inventive 1108 99 98 example 5 Inventive 1 84 99 99 example 6 Comparative 1 343 9998 example A Inventive 10 212 99 95 example 3 Example 4 10 288 98 96Inventive 10 281 99 96 example 5 Inventive 10 252 98 96 example 6

1. A process for preparing carboxylic acid salts, which comprisesreacting alcohols of the general formula IR—CH₂CH₂OH  (I) where R is —(OCH₂CH₂OH) or —NR¹R² and R¹ and R² are eachindependently hydrogen, phenyl, —CH₂CH₂OH, C₁- to C₂₀-alkyl or C₂- toC₅-dialkylamino with an alkali metal hydroxide, alkaline earth metalhydroxide or a mixture thereof in water in the presence of a coppercatalyst which a) consists of copper or b) comprises from 99.9 to 10% byweight of copper and from 0.01 to 90% by weight of iron and from 0 to50% by weight of one or more other metals, and may optionally be doped,prepared by precipitation of copper salt solutions or by coprecipitationof copper and iron salt solutions optionally containing salts of othermetals using a base, and reduction by hydrogen, at temperatures of from120 to 280° C. and a pressure between the vapor pressure of the waterand 75 bar.
 2. A process for preparing carboxylic acid salts as claimedin claim 1, wherein the content of aluminum ions in the reaction mixtureis less than 4000 ppm.